Laminated record



Feb. l1, 1936. B. c, BREN 2,030,568

LAMINATED RECORD Filed Dec. 6, 1955 '@M BY .Y

ATTO EY.

Cil

Patented Feb. 1i, 1936 1 LAMmA'rEn RECORD Bozetech C. Bren, Cedar Grove, N. J., yassignor to Dupont Viscoloid Company, Del., a corporation of Delaware Application December 6, 1 933, Serial No. 701,110

GCIaims. K (CL 154-43) This invention relates to laminated records and the method of making same and, more particularly, to a sound record composed of a relativelyA thick core upon which is superposed on one or both sides a thin playing surface into which surface a sound groove is impressed.

Heretofore records on which vibratory motion is recorded by means of grooves, and particularly sound records, have been made both as a single, homogeneous composition throughout and as a laminated structure having a relatively thick core of one material andv a thin playing surface on one or both sides in the case of a disk record, or merely on the outside in the cylindrical type of record.

Where records of the laminated type have been made,`this has been done for the purpose of improving the mechanical strength of the record and also for the purpose of combining the superior acoustical or wearing properties of one material with the greater strength or cheapness of another material. Although many improvements have been made in records of this type-there has not, as yet, been provided an entirely satisfactory laminated record having good acoustical pr'operties and yet relatively economical to manufacture.

An object of the present invention is to provide a laminated record which is inexpensive and yet possesses properties as good as, or better than, any record heretofore known. A further object is to provide a sound record having superior acoustical properties at a reasonable cost. A still further objectis to provide an economical and simple process of manufacturing laminated records having advantageous properties. .y 'The above objects are accomplished according to the present invention by making a record having a relatively thick core of a filled cellulose 'derivative composition and superposed thereon a thin playing surface of an unfilled cellulose derivative composition; Where a disk record is desired having two playing surfaces, a thin playing surface of an unfilled cellulose derivative composition will be superposed on both sides of the' `Preferred embodiments of the linvention are` Referring to the drawing, reference numeral I designates the relatively thick core of .l the record which, according to the present invention, is composed of a filled cellulose derivative composition;

2 represents the relatively thin playing vsurface 5 superposed on the core `and composed of an unfilled cellulose derivative composition, and '3 represents the sound grooves customarily made on records of this type.

Through extensive research on sound records lo made of various compositions, it has been 'found that cellulose derivatives and in particular cellulose acetate, have unique excellence as material for sound records in that the recordings im'V pressed therein, when played, have been found 15 to have a distinctly superior degree of faithfulness to the original sound and an exceptional freedom from extraneous noise. lvThe superior faithfulness of reproductionLpossible with these substances is probably'attrnibutable to their excellent flowing andmolding properties, which venable them to receive a very accurate and ex- Y act duplication of the sound recording from the matrix. The freedom from extraneous noise in reproduction, i. e., the absence of so-called scratch, or surface, or background noise, is due probably to the complete homogeneity of such material and rits freedom from gritty or brittle constituents. Although the present invention is applicable to cellulose derivative compositions in general, the cellulose acetate compositions, due e to their superiority, are preferred, and-accordlngly the present invention is specifically `de scribedlwith'l respect to this particular ester.

However, in place of cellulose acetate, the-other 'well known cellulose derivatives, such 'as cellulose nitrate, propionate, or the various ethers, such as ethyl cellulose, benzyl cellulose, and similar ethers, may be employed.

Although it has been discovered that cellulose 4o acetate is outstandingly suitable for the manufacture of high grade sound records, this compound is subject to the objection of hygroscopicity, with the result that a thin sheet record of cellulose acetate composition is subject to the disadvantage of warping with changes in atmos-v pheric conditions. It is desirable, therefore, that records of cellulose acetate composition be made of relatively large thickness and this results in a rather high material co'st per-frecord where a 50 homogeneous cellulose aceate record with no filler,

Y or very little filler, is used.

According to the present invention, it has been found that the unparalleled acoustical adrian-" tages of unlled cellulose acetate composition may be retained absolutely unimpaired, but nevertheless the cost of the record appreciably reduced, by using instead of a solid, homogeneous record of unfilled cellulose acetate composition,v a laminated record comprising a core molded from a celluloseA acetate composition of high ller content and then super-posing on said core a relatively thin playing surface composed of an unfilled cellulose acetate composition. Ihe method of manufacturing these records is subject to wide variation, but it is preferred to make up the filled cellulose acetate composition as a powder and mold it according to well known methods by the application of heat and pressure in a suitable die to form the core, and then to superpose on one or both sides of said core a thin layer or sheet of the unfilled cellulose composition and weld the two laminations together by the application of heat and pressure. This is accomplished preferably in the customary record die proper so that the application of the thin playing surface to the core and the imprinting of a sound recording upon the playing surface may be accomplished simultaneously. However, it is obvious that the playing surface and core may be welded together in a die having no sound recording thereon, thereby producing a blank record upon which the sound recording may be impressed at a later time in a separate operation.

The molding and processing operations herein referred to have been long known to the art and those skilled in this art would readily understand that, depending upon the specific formula of the compositions used, conditions of pressure and temperature will be varied in accordance with known practice. However, it should be noted that these cellulose acetate compositions used both for the core and the thin playing surface are thermoplastic and may be welded together merely by the application of heat and pressure without the use of auxiliary adhesives and, in the preferred embodiment of the invention, the record is made in this manner because the finished article is appreciably better in acoustical properties and freedom from warpage.

The core material, according to the present invention, is composed essentially of cellulose acetate, plasticizer, and a relatively high proportion of filler, the latter greatly reducing the material cost of the record and, if anything, improving the quality of the record.

The following examples are given to illustrate specific formulas of material adapted for use in the core, parts being given by weight:

Example 1 Parts Cellulose acetate Triphenyl phosphate 17 Dimethyl phthalate 25 Wood our 100 Pigment 17 Example 2 Parts Cellulose acetate 100 Triphenyl phosphate 25 Dimethoxy ethyl phthalate 42 Wood pulp 67 China clay 83 Pigment -xample 3 Parts Cellulose acetate 100 'Irlphenyl phosphate 19 p-Toluene sulfonamide 15 Ethyl p-toluene sulfonamide 19 Cottonseed hull ber 123 Pigment 6 Example 4 Parts Cellulose acetate 100 Triphenyl phosphate 10 Dimethoxy ethyl phthalate 40 Wood our 75 China clay 75 Pigment 12 Example 5 Parts Cellulose acetate 100 Triphenyl phosphate 12 Dimethoxy ethyl phthalate 50 Wood flour 100 China,clay 100 Pigment 12 Example 6 Parts Cellulose acetate 100 Triphenyl phosphate 12 Dimethoxy ethyl phthalate 32 Wood flour 286 Pigment 9 It is preferred that in these compositions for the core, the following range of proportions be observed (parts by weight) '1 Parts Cellulose acetate 100 Plasticizer 144 to 62 Filler 123 to 286 flour is a satisfactory and preferred filler. With respect to the proportions in the core composition, these may be varied considerably as is well known in the art. In order to effect any appreciable economy in the cost of material used in the record, the percentage of filler should be high, and preferably this should range from a ratio of 100 parts by weight of cellulose acetate to 75 to 300 parts by weight of ller, the preferred formula for records of a certain type being readily determined according to the ordinary practice in the cellulose derivative plastic art. The addition of pigment is usual in such compositions but is not necessary.

'I'he following examples illustrate typical formulas for the cellulose acetate material to be used in the thin playing surface, parts being given by weightz- Dimethyl phthalate 12 It is preferred that in these compositions for the playing surface the following range of proportions be observed (parts by weight) Parts Cellulose acetate 100 Plasticizer 43 to 17.5

AIt will be noted that in the above examples no iller is used,` and therefore, that the playing surl face of the records according to the present invention is essentially composed of a cellulose derivative, preferably the acetate, and a plasticizer.` A small amount lof coloring matter may beemployed if desired. As those skilled in this art will understand, not only the plasticizers disclosed in the above examples may be used, but

, other plasticizers known in this art may be sub- .stituted in part or wholly, and likewise mixtures of such plasticizers may be used. The proportion of plasticizer to cellulose acetate will be varied in order that the exact degree of hardness and flexibility desired for making records of particular types maybe obtained.

According to this invention, the unlled cellulose acetate compositions illustrated above are worked up into` sheet form according to usual practices and used as such in making the laminated record, whereas itl is preferred to make the core by using the filled molding material as a powder, although sheets or fragments may likewise be used to fill the mold wherein the core is to be made by the application of heat and pressure.

as the acoustical properties of therecord are considerably improved if the thickness of the playing surface is great enough so thatwhen the sound groove is impressed upon the playing surfacethe groove will not b e transmitted by the playing surface through to the core to any appreciable extent.

'I 'he specific examples of compodtions have been. given with respect to cellulose acetate, but it is-v to be understood that the invention in its broader phases also'includes the use of other cellulose derivative compositions and the formulation of specific compositions of the other cellujlose derivatives involves no more than the skill ofthe ordinary worker in this art, as long as the essential features of the invention are observed.

namely, that the core material be highly illled, vwhereas'the material to be used as a playing surface be an unfilled composition.

The present invention is directed primarily to the production of sound records of the disk type, but is is to be understood that it is also applicable to any other technique in which vibratory motion is recorded by means of grooves. It is by no means necessary that the record be in disk form, as the invention is equally applicable to 'the commonly used cylindrical records.

' An advantageof the present invention lies in the fact `that the herein described laminated records secure the superior acoustical advantages of a relatively thick record of an unfilled cellulose acetate composition without the excessive cost of ysuch a record, this being due to the fact that the use of a highly filled molding oomposition with a base of cellulose acetate as the core of the record has the unexpected result of leaving unimpaired the acoustical advantages of the unfilled cellulose acetate playing surfaces. This advantage is likewise true, although to a more limited extent; in records made from other cellulose derivative compositions. The fact that the acoustical properties of the unlled cellulose acetate playing surface remain unimpaired is most unexpected, since a laminated record made with a cellulose acetate playing surface but a core other than a cellulose acetate lled composition core badly impairs the acoustical advantages of the playing surface. Likewise, if the playing surface is not appreciably thicker than the depth of the sound groove the acoustical properties of the record are also impaired. Another advantage of the herein described records lies in the fact that adhesion of the laminations is obtained by the application of heat 'and pressure alone, andthis omission ofauxiliary`adhesive not only provides a more economical process in laminating, a step in the compositing operation, but also has the advantage of eliminating a frequent cause of warpage.

In both the molding of the core and the weld-` varied considerably. as the formulation of the z\compcsitions is changed. However, it has been found that a pressure of about 1500 to 3000 pounds'per square inch and a temperature of 130 to 175 C. is usually satisfactory'. It will be understood that the present invention is not to be limited to such temperatures and pressures and, in its broader phases, even includes the use of an auxiliary adhesive whereby the laminations A- may be united without employing heat at all.

As many apparently widely different embodiments of this invention may b e made v without the spirit and scope thereof, itis' that the invention is not limited l. A laminated sound record comprising a relao tively thick core of a homogeneous cellulose ace tate composition containing iinely divided filler and a thin playing surface of an unillledcellulosel acetate composition.

" 2. A laminated sound record comprising a relatively thick core of a homogeneous'cellulose'ace- I tate composition containing finely ',divlded -ller and a thin playing surface of an unfilled cellulose -ller and a thin playing surface of an unfilled cellulose acetate composition, said core and playing surface being united without an intermediate adhesive layer and the thickness of said playing surface being appreciably greater than the depth of the sound groove impressed thereon.

4. A laminated sound record comprising a relatively thick core composed essentially of cellulose acetate, plasticizer, and uniformly distributed nely divided filler, and a thin playing surface composed essentially of cellulose acetate and plasticizer.

52,080,568 acetate composition, said core and playingsur- 5. A laminated sound record comprising a relatively thick core composed essentially o f vcellulose acetate, plasticizer, and uniformly distributed finely divided filler, and a thin playing surface composed essentially of cellulose acetate and plasticizer, said core and playing surface being united without an intermediate adhesive layer.

6. A laminated sound record comprising a relatively thick core composed essentially of cellulose acetate, plasticizer,v and uniformly distributed iinely divided illler, and a thin playing surface composed essentially of cellulose acetate and plasticizer, said core and playing surface being united without an intermediate adhesive layer and the thickness of said playing surface being appreciably greater than the depth of the sound groove impressed thereon.

y BOZETECH C. BREN. 

